1. Field of the Invention
This invention pertains to the use of powdered graphite on the lip seal of an air damper to cause the air damper to operate more smoothly.
2. Description of the Prior Art
In the prior art, an air damper of the type with a piston shaft and a lip seal reciprocating within a body or cylinder is well-known. However, a typical rubber seal may slide roughly, particularly at low speeds, resulting in a rough operation of the air damper. Many coatings may attract dust or plug the air orifice thereby impairing the function of the air damper. Moreover, the use of grease or silicone may cause the seal to stick in place and not open. Moreover, the viscosity of grease increases under cold conditions which slows down the damping rate.
An elastomeric coating for a lip seal is disclosed in U.S. Pat. No. 4,818,620 entitled xe2x80x9cElastomer Coated Lip Sealxe2x80x9d, issued on Apr. 4, 1989 to Pilkington, but does not adequately address the above deficiency.
Graphite powder for lubrication purposes is likewise old in the prior art, such as is disclosed in U.S. Pat. No. 5,702,769 entitled xe2x80x9cMethod for Coating a Substrate with a Sliding Abrasion-Resistant Layer Utilizing Graphite Lubricant Particlesxe2x80x9d, issued on Dec. 30, 1997 to Peters but does not address the above deficiency with regard to smoothness of operation.
It is therefore an object of this invention to provide for increased smoothness of operation of an air damper, particularly at low speeds.
It is therefore a further object of this invention to achieve the above object without any impairment of the function of the air damper, such as attracting dust or plugging the air orifice.
It is therefore a further object of this invention to achieve the above objects without unduly increased manufacturing expenses or other deficiencies.
These and other objects are achieved by providing a rubber or thermoplastic elastomer lip seal coated with a minimum of 0.5%/seal part weight graphite powder/molybdenum disulfide. Typically, the lip seal is made of rubber or thermoplastic elastomer impregnated with a minimum of 3% molybdenum/seal part weight, or a minimum of 2% TEFLON(copyright) (polytetrafluoroethylene) or silicone/seal part weight. The housing is typically made with a minimum of 2% silicone impregnated thermoplastic.